For Hesselius, the reverend’s choice of hot drink is central to his downfall. The story is called “Green Tea” – indicating the key role the substance has in the story.

When Le Fanu’s tale was published tea-drinking had become popular in Britain. But there was still a mistrust of oriental tea growers and packagers – particularly those involved with green tea – who were often accused of adulterating or contaminating the product. It’s foreign-ness makes the reverend’s favourite beverage suspiciously exotic – and dangerous.

As for the second reason, a fondness for “pagan” books – Hesselius admits he shares his patient’s (at the time relatively novel) interest in non-Christian philosophy. So reading them hardly seems a reason for the poor man’s life-destroying delusions.

It’s hard to avoid the conclusion that the reverend isn’t really guilty of any serious wrongdoing -apart from drinking tea and staying up late. Certainly not enough to warrant his terrible hallucinations and torments.

But in the light of Hesselius’s diagnosis it’s hard to avoid somehow blaming Jennings.

Which is one of the cruel things about this type of psychological horror. Monstrous, even.